Kidney infection: Everything you need to know

A kidney infection, also known as a renal infection or pyelonephritis, is usually caused by a urinary tract infection (UTI) that has bacteria wandering up your urinary tract until they reach one or both of your kidneys. Only about 1 in 30 UTIs actually leads to a kidney infection, however, so there’s no need for you to panic. But how do you know whether you’re suffering from a kidney infection or not?

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What are the symptoms of a kidney infection?

If you’re suffering from a kidney infection, your symptoms will generally come on quite quickly; usually anywhere between a few hours and a couple of days. You might experience one or more of the following symptoms:

  • Chills
  • Feeling nauseous
  • Pain in your abdomen, back, groin, or side
  • Vomiting
  • Having to pee often

In addition to the symptoms of a kidney infection, you might also be experiencing symptoms of a UTI. If that’s the case, you might have some of the following:

  • Feeling like you need to pee after you just went
  • Smelly, cloudy, or bloody pee
  • Burning or stinging pain when peeing
  • Thick white to yellow liquid in your pee (pus)

Children under the age of 2 that are suffering from a kidney infection might only have a high fever as a symptom. If you’re 65 or older a kidney infection might only cause symptoms like confusion and trouble speaking.

If your kidney infection isn’t treated properly or remains completely untreated, it might cause you to develop sepsis. This is a life-threatening condition where the infection of your kidneys makes its way into your bloodstream. Possible symptoms of sepsis are:

  • Rash
  • Fever & chills
  • Rapid heart rate and breathing
  • Confusion


What can cause a kidney infection?

Generally, a kidney infection is caused by bacteria from your intestines that enter your urinary tract via your urethra. If the bacteria enter your urinary tract, they can multiply and spread first to your bladder and then to your kidneys. But how do they end up in your urinary tract in the first place? They can easily be transferred via sexual intercourse or if you’re wiping back to front when you go to the loo.

However, bacteria entering your urinary tract via your urethra isn’t the only possible way how you can end up with a kidney infection. Other, less common causes, include:

  • Diabetes
  • A blockage in your urinary tract like a kidney stone, tumour, or an enlarged prostate in men
  • Bladder or kidney surgery
  • An unusually shaped urinary tract
  • A weakened immune system


Who’s most at risk of developing a kidney infection?

  • You’re also more at risk if you’re wearing an indwelling urinary catheter.
  • If you have any damage to your spinal cord or nerve damage to your bladder, you might not notice that you have a UTI which can lead to a kidney infection.
  • If you’re pregnant, your urinary tract shifts a little which can also make it easier for bacteria to get into your kidneys.
  • If you’re a woman, you’re more at risk of developing a kidney infection as your urethra is much shorter and very close to your anus. This makes it easier for bacteria to reach your urinary tract.
  • If you have a weakened immune system or if you’re taking immunosuppressant drugs you develop kidney infections more easily.
  • If you’re unable to empty your bladder fully, also known as urinary retention, you’re more at risk.
  • If you suffer from vesicoureteral reflux (VUR) you’re more likely to develop kidney infections. This is a condition where your urinary tract allows urine to flow backwards into your kidneys rather than out via your urethra.


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How is a kidney infection diagnosed and treated?

If you think that you’re suffering from a kidney infection or have blood in your urine, it’s super important that you speak to your doctor. But how is a kidney infection diagnosed and what can be done to treat it?


Your GP will likely ask you some questions about your medical history & symptoms and they’ll probably also give you a physical once-over. They might also perform some tests which can include the following:

  • Urinalysis: They might check your urine sample under the microscope for bacteria and white blood cells.
  • Urine culture: Your GP probably sends your urine off to a lab for culturing to determine which specific bacteria it is that causes your infection.
  • Rectal exam: If you’re a man, your GP might check whether your prostate is enlarged and blocking your bladder neck.
  • They might also perform a CT scan, MRI, or ultrasound test to provide images of your kidneys.



How your kidney infection is treated fully depends on how severe it is. If it’s a mild infection, you’ll likely be treated with oral antibiotics; if it’s more severe, you might need some IV antibiotics. If your GP prescribes oral antibiotics, you’ll likely need to take these for 2 weeks and you might be prescribed a follow-up urine culture to make sure the infection has fully disappeared. If it hasn’t cleared, you might be prescribed a second course of antibiotics. A kidney infection can be very painful so talk to your GP about getting some painkillers prescribed if you feel like you need them.

If your kidney infection is severe, there’s a chance that you have to stay in hospital for some IV antibiotics and fluids. Usually, your symptoms will improve very soon after starting treatment. It’s super important that you finish your course of antibiotics, even if you’re feeling better, though! This is to make sure your kidney infection doesn’t come back.

What are possible complications of a kidney infection?

If your kidney infection isn’t treated properly or remains completely untreated, there’s a chance that you can suffer serious complications.

  • There’s a chance that you might suffer permanent kidney damage. This can lead to kidney disease and (very rarely) to kidney failure.
  • The bacteria can move into your bloodstream where it can potentially cause you to develop sepsis.
  • When pus accumulates in your kidneys, you can develop an kidney abscess. Symptoms include bloody urine, weight loss and pain in your abdomen. Sometimes, these abscesses need to be drained in a surgical procedure.


Can you prevent a kidney infection?

The only way to definitely prevent a kidney infection would be to keep 100% of all bacteria out of your urinary tract. That’s generally not possible, but you can take certain steps to keep your urinary tract as bacteria-free as possible.

  • Try and go for a pee after you had sex to flush out any bacteria that might’ve made it into your urethra.
  • If you need to pee, go to the loo without holding it in.
  • Don’t use any deodorant sprays or douches on your genital area.
  • Drink plenty of fluids; 6 to 8 glasses of water is a good amount.
  • If you’re suffering from constipation, make sure it’s treated as leaving it untreated greatly increases your chance of developing a UTI.